Many electronic still cameras are well known which are adapted to record an object as digital image data. An image formed through an optical system is converted into electrical signals by a photoelectric conversion element such as a CCD or the like, these electric signals being then recorded in a storage medium within the camera body. The image data thus recorded can be easily edited or processed by an electronic instrument since they are in digital form, unlike the conventional camera images. Auxiliary units utilizing such a feature have been developed. Among then, a hard disc unit will be described which is used to store a mass of image data.
The electronic still cameras convert the taken image into digital signals which are in turn stored in a memory within the main body of the camera, which memory will be simply referred to as "main body memory". In general, such a memory has a capacity that cannot store many images. If the number of taken images reaches a given level, they must be transferred to another storage medium. Thus, the electronic still cameras usually contain a floppy disc drive to which the stored image data are often transferred from the main body memory. Floppy discs are light-weight, cheap and convenient for subsequent editing.
However, the floppy disc is also naturally restricted in capacity. If a number of high-resolution images, each having a large amount of data, are to be recorded, still another storage medium having a much greater capacity is required. Hard discs meet such a requirement With the development of storage systems and manufacturing techniques, it has recently become possible to provide a hard disc of cigarette-case size that has a capacity exceeding 100 MB. Such a capacity corresponds to that of 100 floppy discs. When the floppy discs are replaced by such a hard disc, the number of images that can be taken by the electronic still cameras is hugely increased.
The hard disc used as an auxiliary unit in the electronic still camera was developed aiming at such an advantage. Since the hard disc is relatively compact, for example, it may be connected to the bottom of the electronic still camera such that taken image data will be appropriately recorded therein. As a result, the number of images to be recorded can be hugely increased while maintaining the main body memory physically small. With future development of various auxiliary units, including hard disc units, it is expected that the application and possibility of electronic still cameras will be further widened.
As described, electronic still cameras were released from the restriction relating to the number of images to be recorded through merchandising of hard disc units. The development of such an auxiliary unit raises another new problem due to the conventional programs for controlling the auxiliary unit which have been stored in the main body memory and normally in ROE. Such a problem will be described with reference to the drawings.
FIG. 1 is a schematic view of an electronic still camera system that comprises an electronic still camera and an auxiliary unit.
Referring to FIG. 1, an auxiliary unit 4 is connected to the bottom of an electronic still camera 2 such that data can be transmitted and received therebetween through data and control buses 6, 8.
The electronic still camera 2 contains a microcomputer 10 for controlling the entire system. A program to be executed by the microcomputer 10 has been stored in ROM 12. The ROM 12 may be included in the microcomputer 10.
The electronic still camera system also comprises a user interface section 14 on which a plurality of control buttons 16 for a user to command various operations in the system are provided. On sequentially depressing these control buttons 16, a procedure 18 such as interruption is initiated. Thus, the microcomputer 10 reads the necessary program routine from the ROM 12 which in turn executes the user's command.
FIG. 2 is a memory map for illustrating the internal structure of the ROM 12.
As shown, the ROM 12 comprises at least a basic processing area 20 for starting up the system and carrying out the basic operations of the camera and an extended processing area 22 which stores a program for controlling auxiliary units. The extended processing area 22 is formed by areas 22-1, 22-2 . . . 22-n which correspond to program areas for the auxiliary units 1, 2 . . . n.
Problems are raised in the above arrangement because of the provision of the extended processing area 22 within the ROM 12. The problems will be described from a plurality of viewpoints.